WO2003032710A2 - Method for treating material at a high altitude - Google Patents

Method for treating material at a high altitude

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Publication number
WO2003032710A2
WO2003032710A2 PCT/EP2002/011362 EP0211362W WO03032710A2 WO 2003032710 A2 WO2003032710 A2 WO 2003032710A2 EP 0211362 W EP0211362 W EP 0211362W WO 03032710 A2 WO03032710 A2 WO 03032710A2
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WO
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Application
Patent type
Prior art keywords
laser
light
beam
pulse
high
Prior art date
Application number
PCT/EP2002/011362
Other languages
German (de)
French (fr)
Other versions
WO2003032710A3 (en )
Inventor
Ludger Wöste
Roland Sauerbrey
Jean-Pierre Wolf
Original Assignee
Freie Universität Berlin
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Classifications

    • AHUMAN NECESSITIES
    • A01AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01GHORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
    • A01G15/00Devices or methods for influencing weather conditions
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S3/00Lasers, i.e. devices for generation, amplification, modulation, demodulation, or frequency-changing, using stimulated emission, of infra-red, visible, or ultra-violet waves
    • H01S3/005Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0057Temporal shaping, e.g. pulse compression, frequency chirping

Abstract

According to the invention, material can be treated at a high altitude from the ground by means of a filament which is oriented towards the sky and is produced by means of the self-focussing and self-defocussing of a highly intensive laser beam. A laser pulse is produced by means of a pulse laser. Said laser pulse is emitted into the atmosphere from the earth. The laser pulse is temporally and spatially focussed in such a way that, in a zone in the atmosphere, the peak performance of the laser pulse exceeds the critical performance necessary for the laser pulse to have a self-focussing effect in the air, in such a way that a filament is formed by the laser pulse. Said technique can be used, for example, to produce condensation cores in the atmosphere and to produce an artificial light source at a high altitude, e.g. for calibrating telescopes.

Description

A method of manipulating matter at high altitude

technical field

The present invention relates to a method for influencing matter out at great height from the ground. There are various applications. It is important to find a medium that is able to act on the matter from the ground at high altitude with sufficient energy.

Disclosure of the Invention

The invention is therefore based on the object, matter in a great height from the ground to apply with sufficient energy and energy density and influence in order to achieve desired technical effects.

According to the invention this object is achieved in that the influencing takes place by means of a signal generated by self-focusing high intensity laser beam and -defokussierung directed against the sky filament.

By a filament a focused high-energy beam with kleinerm opening angle large insert can be guided so that it at transmission from the

Ground still has a high energy density from which exerts significant effect on existing there matter.

One application of the invention is the generation of condensation nuclei for rain in the atmosphere. The formation of raindrops atmospheric condensation nuclei are often required even at high humidity at which the water condenses. It may happen that air masses flowing away with high humidity over a land without it rains, and only later, abregnen example of mountain ranges.

Another serious problem is hail. Hail is formed in clouds, where significant updrafts and downdrafts prevail. A water-crystal core passes from the cold upper regions in warmer deeper areas of high humidity. In these areas, water is reflected and freezes on the crystal nucleus when the assembly is supported by the rise again in higher layers. By repeated up and

From, larger hailstones that eventually become so heavy that they are no longer carried by the winds and fall to the ground form. By hail can cause significant damage, in particular crop damage occur.

Attempts have been made to provide in such humid air masses artificial condensation nuclei and thereby cause rain in desired regions. It has also been tried to avoid hail over lived or developed areas characterized in that the humidity is brought to the formation of artificial raining by condensation nuclei. Such a method is to sprinkle with airplanes rain clouds with silver iodide crystals as condensation nuclei and thus to bring a lot of rain. The sprinkling of clouds with silver iodide crystals takes place "on suspicion", without precise knowledge of whether in fact there are steam supersaturated humid air masses. This process is expensive and of limited effectiveness.

The invention has for its specific object to provide a method for effective

to create generation of condensation nuclei in the atmosphere.

This object is achieved by a method of the aforementioned type comprising the following steps:

(A) generating a laser pulse by means of a pulse laser, (b) emission of the laser pulse from the earth in the atmosphere, and

(C) temporal and spatial focusing of the laser pulse so that the peak the critical power for self-focusing effect of the laser pulse exceeds power of the laser pulse at a location in the atmosphere in air.

When a high intensity laser pulse ültrakurzer is transmitted (in the femtosecond and Terawattbereich) in the atmosphere occur nonlinear optical effects. Due to the occurring high field strengths, the refractive index of air molecules also is enhanced by the Kerr effect. Since the intensity profile of the laser beam over the cross section of the laser beam across approximately bell-shaped, this increase in refractive index and thus the reduction of the speed of light at the edges of the laser beam is smaller than the laser beam in the central region. The air acts in this area extremely high field strengths as a converging lens. Thereby, the laser beam is focused. This focus of the already high intensity

Laser beam occurs to an extremely high energy density, which leads to a multi-photon or field ionization of the air. The ionization also results in a change in the refractive index of the air. This change in refractive index also depends on the light intensity, but the refractive index is decreased with higher light intensity here. Since the profile of the light intensity of the focused laser beam corresponds again over the cross section of the laser beam away as a bell curve, the ionized regions act as a divergent lens. The laser beam is defocused again. Thus, a state in which the described Kerr effect effectively and the laser beam again results again is focused. There is thus alternately focusing and defocusing of the laser beam as by alternately arranged converging and diverging lens, on the basis of the respective states of the laser beam itself. There is a "self-focusing" and "Selbstdefokussierung". This leads to an over long distances is not substantially diverging, as determined by the pulsed, high-intensity laser light beam tube of, for example 100 microns in diameter with ionized sections. Refers to such caused by the laser beam state as "filament". Theoretical considerations of the interaction of these effects include in the publication "Self-channeling of high-peak-power femtosecond laser pulses in air" by A. Braum et al. in Opt. Lett., Vol. 20, No. 1, pp 73-75 (1995), and in the publication "The critical laser intensity of self-guided light filaments in air" in Appl. Phys. B, Vol. 71, pp 877-879 (2000) listed.

The invention is based on the recognition that such filaments are suitable with their ionized portions trigger as condensation nuclei for the formation of high humidity air raindrops. This is an effect similar to a cloud chamber, where water vapor-saturated air is caused by the generated particles such as α-rays ions to form droplets, and then a web of

will make particle visible. It has been found that such a "filament" sufficiently bundled over relatively long distances to the humid air masses can be guided.

Another application of the invention is the creation of artificial light sources at a great height, in particular for the calibration of astronomical telescopes with respect to atmospheric interference.

The beam paths astronomical telescopes out an atmospheric aberration by the terrestrial atmosphere. The atmosphere acts as an optical member before

Telescope, which brings lens aberrations in the picture. This lens aberrations change with the state of the atmosphere and the position of the object. It is desirable to determine these atmospheric aberration from case to case and be able to correct obtained from the telescope images of celestial objects accordingly.

The object is to generate an artificial light source of known position in height, above the actual atmosphere.

This object is achieved by the method steps:

(A) generating a filament produced by self-focusing and -defokussierung a high intensity pulsed laser beam directed against the sky, which produces a white continuum radiation in the longitudinal direction of the filament, wherein an artificial light source occurs at high altitude by excitation of meteorites dust,

(B) measuring the pulse transit time of the backscattered from the artificial light source with respect to the emitted laser pulses of the pulsed laser beam and

(C) determining the real position of the artificial light source from the direction of the filament and the pulse duration of the backscattered radiation from the artificial light source

In such "filaments" as they were described above, there occurs another phenomenon: it creates white light, ie, a continuum radiation extending over a wide wavelength range. This white light is emitted substantially in forward and backward direction of the filament. This phenomenon is known (OPTICS LETTERS, 2001, Vol. 26, No 8, 533-535). It is also known to use this white light as the light source for the spectral analysis of the atmosphere.

The invention is based on the recognition that this white light emitted in the forward direction of the filament above the atmosphere in 80 to 120 km altitude present there meteorite dust can stimulate fluorescence, in the different wavelengths, in which fluoresce the different substances contained in the meteorite dust. It is then produced by the fluorescent radiation an artificial light source at this level with a broad spectrum of wavelengths. The exact

Position of the artificial light source are determined in that the pulse duration of the backscattered from the artificial light source is measured with respect to the emitted laser pulses of the pulsed laser beam and the real position of the artificial light source from the direction of the filament and the pulse duration of the backscattered radiation is determined. The laser beam consists of a series of high-intensity

Laser pulses in Terawattbereich of very short pulse duration on the order of femtoseconds. Accordingly, there is also the white light generated from the respective light pulses and the stimulated emission of the artificial light source is pulsed accordingly. From the pulse propagation time between light emitted laser pulse and the pulse of light of the backscattered light, the exact position of the artificial light source can be determined along the filament.

The artificial light source can be utilized for various purposes measurement.

One application of the invention is related to the correction of imaging errors by the atmosphere of an astronomical telescope. This application is characterized by the steps of:

(A) observing the artificial light source by means of the telescope to be calibrated,

(B) determining the image supplied from the telescope of the artificial light source and

(C) correcting the images produced by the telescope with respect to imaging errors by comparing the real position of the artificial light source and the image provided by the telescope.

The artificial light source which is located above the atmosphere and at its observation also atmospheric aberration occurs can then be used in this manner for calibration of astronomical telescopes. Because the location of the artificial light source is known, from an offset of the apparent position of the light source artificial respect to its real position of the atmospheric-related

Aberrations are determined. This also chromatic aberrations can be determined because the artificial light source emits a broad spectrum of wavelengths. Thus the corrected for atmospheric induced aberrations position of an observed in the vicinity of this artificial light source sky object can be determined.

Embodiments of the invention are subject of the dependent claims 3 to 5 and 7. Embodiments of the invention are explained in more detail below with reference to the accompanying drawings.

Brief Description of Drawings

Fig.l is a schematic diagram illustrating the formation of the

Filament by a pulsed high intensity laser beam.

2 illustrates the formation of a "convex lens" by the intensity profile over the cross section of the laser beam and caused by the Kerr effect change in the refractive index of the air.

3 illustrates the formation of a "negative lens" by the intensity profile over the cross section of the focused laser beam and the ionization caused by change in the refractive index of the air.

4 is a schematic representation of an apparatus for generating

Condensation nuclei in moist air masses that will be caused to raining.

5 is a schematic representation of the generation of very short, high intensity

Laser pulses.

6 shows schematically a pulse stretcher ( "stretcher") to produce a spectral fanning of the laser pulse.

7 shows schematically a pulse compressor to produce a short, high-intensity laser pulse. Figure 8 illustrates the formation of a very short laser pulse in

Femtosecond and Terawattbereich of an emitted laser pulse with "negative chirp".

9 shows the generation of an artificial light source at a great height to

Calibration of a telescope.

Preferred VERSIONS OF THE INVENTION

In Figure 4 is indicated 12 10 high energy with a laser assembly for generating a sequence of laser pulses. The laser pulses have a "negative chirp", ie they are spectrally fanned out ( "chirp"), the slower running in the propagation medium wavelengths, the leading edge of the laser pulse, and the faster running in the propagation medium wavelengths form ( "negative chirp, the trailing edge of the laser pulse "). By an adjustable telescope 14, the pulsed laser beam is directed onto a mass of air of high humidity in form of a cloud 18th

The group velocity of the spectrally fanned laser pulses in the air as a propagation medium comprises a dispersion (GVD). Short Wavelengths run slower than longer wavelengths, since the refractive index in the air is larger for short wavelengths than for a long time. This provided the spectrally fanned out and a "negative chirp" emitted laser pulse when passing compressed by the air. The longer wavelengths at the leading edge of the Laseipulses be "obtained" from the shorter wavelengths that form the trailing edge of the spectrally fanned laser pulse. The laser pulse becomes shorter and more intense. The point 20 in which this happens, is located at a distance from the telescope fourteenth

This compression of the laser pulse for a particular path through the propagating medium air is shown schematically in Figure 8: At 22, a spectrally fanned laser pulse is denoted by "negative chirp". The faster running shorter wavelengths are in the region of the rear edge 24 of the fanned laser pulse 22. The slower running longer wavelengths are in the range of the leading edge 26 by group velocity dispersion GVD of the laser pulse is for a path 28 to a steep laser pulse 30 in the femtosecond range with high performance compressed in the range of terawatts.

Figure 5 to 7 show schematically the generation of the emitted laser pulse and the generation of the "negative chirp".

A laser 32 generates a sequence of laser pulses 34 of for example, 80 fs low energy of, for example 6 nJ with a frequency of for example 8 10 7 Hz. In a pulse stretcher 36, these laser pulses are in spectrally fanned, relatively long laser pulses 38 ps of, for example 200 time and low intensity 2-3 nJ, also reacted with a frequency of 8 10 7 Hz. A regenerative amplifier 40 selects from individual pulses and amplifies this ps to pulses 42 of 200 length and average energy of for example 5 mJ at a frequency of eg 10 Hz. This laser pulses 42 are amplified by an amplifier 44 having s several passages to laser pulses high energy of for example, 400 mJ amplified, with pulse duration and frequency remain unchanged. The laser pulses 46 thus obtained, spectrally fanned are then compressed by a compressor 48 in very short and very intense laser pulses 22 from the laser assembly 10 (Fig.4) is emitted. The compressor 48 is, however, in this case designed so that the emitted

Laser pulse 22 still has a "negative chirp" that is spectrally still remains fanned such that the short wavelengths in the region of the rear edge of the laser pulse 22 and the longer wavelengths in the region of the leading edge of the laser pulse to occur.

6 shows schematically the structure of a pulse stretcher 36th

The Laseφuls 34 falls into the high-order to a grating as a beam 52 takes place at the grid 52, a wavelength dependent diffraction of the laser light. The diffracted light, as shown schematically, collected by lenses 54, 56 on a second grid 58th

Through the second grid 58, the light of different wavelengths is superimposed back to a spatial beam 60th Since the different wavelengths but have passed through different geometric path lengths between the gratings, the Laseφuls 38 is widened in the beam 60 and spectrally fanned. The beam 60 is then deflected by a mirror 62nd The Laseφuls 38 in the beam 60 then experiences the processing by the amplifiers 40 and 44 of Figure 5 and then falls as Laseφuls 46 to the compressor 48th

The compressor 48 is iri Fig.7 schematically illustrated.

The compressor 48 also includes two gratings 64 and 66 and a mirror 68. The Laseφuls 42 falls as a beam 70 on the grating 64 and is diffracted there wavelength dependent. The spatially spectrally fanned out to the grid 64 beam 70 incident on the second, parallel to the first grid 66. By the second grating the different wavelengths are so bent that a bundle to each other and parallel to the beam 70 beam is formed, each of which is associated with specific wavelength. The rays of this beam are reflected by the mirror 68 in and recombined spatially by the two gratings 64 and 66 to a return beam. In this arrangement, the distance traveled by the rays -schnellenkurzwelligen geometric path length is longer than the long wavelength of the slower jets. This results in a compression to the intense but brief Laseφuls 22. The compressor 48 may however be designed and adjusted, if necessary, that in the pulse 22, a "negative Chiφ" remains, so that there can be a running distance-dependent additional compression by the different refractive indices, as discussed in conjunction with Figure 8.

In a high energy density and field strength in the range of the Laseφulses

Femtosecond pulse duration and Terawatts power as at point 20 (Fig.4) be achieved occur nonlinear optical effects. By the Kerr effect in the air, a self-focusing. The air acts in an area such as a converging lens. Through the self-focusing a very high energy density occurs, which leads to ionization of the air. The ionization results in regions that act as a diverging lens. The so re-diverging laser beam having a lower energy density produced again by the Kerr effect acting as a converging lens area, etc. There is thus alternately a self-focusing of the laser beam and -defokussierung

This is illustrated schematically in FIGS. 1 to 3

In Fig.l are 70, 72 and 74, etc. "collecting lenses" hereinafter, as they are formed by the propagation medium is air by the Kerr effect at a high field strength of the Laseφulses 30th Between these collecting lenses are characterized by the ionization of the air "diverging lenses" 76, 78, etc. formed. The laser beam 14 undergoes by the induced by the Kerr effect "collecting lenses" 70, 72, 74 etc. each have a focusing.

The obtained by the focusing extremely high power density causes a respective ionization of the air, which affects such as "divergent lenses" 76, 78, etc., and causes a defocusing. The laser beam is by self-focusing and - defocusing out largely without divergence. A so-guided laser beam having high intensity and ultrashort Laseφulsen is referred to as "filament".

2 illustrates the formation of the Kerr "collecting lenses". The intensity and field strength of the laser beam is not constant over the entire cross section of the laser beam. Rather, it follows a bell shaped profile as represented by curve 80 to the left in Fig.2. This field strength effected by the Kerr effect, an approximately proportional to change in the refractive index of the propagating medium, so that the refractive index of a positive change over the cross section of the laser beam away also by a bell-shaped profile, The positive change Δnκ e _τ is shown in the middle of Figure 2 by curve 82nd Therefore, the refractive index is less than in the central region at the edge of the laser beam. The

Edge beams run faster than the central beams. That is the effect of a convex lens 70, as shown on the right in Figure 2.

In the focused laser beam, the intensity or power density varies over the cross section of the laser beam away to a bell-shaped profile, which is shown in Figure 3 by a curve 84th Caused by the laser beam ionization also follows this substantially bell-shaped profile and, accordingly, caused by the ionization change Δnι is on. the refractive index., which is represented by curve 86. However, this change is negative. The refractive index is at the edge of the focused laser beam greater -or- less vermindert- than in the middle. The edge beams run slower than the central beams. This corresponds to a diverging lens 76 and causes defocusing.

In Figure 4, the filament thus produced is shown in dashed lines and designated by the 88th can be achieved by suitable choice of the "negative Chiφ" that is compressed only in a region lying at a distance from the laser assembly 10 and the telescope 14 point of Laseφuls 30 so that sufficient for the formation of the filament field strength is achieved. Thus the filament 88 extends from the point 20th The filament is conducted to the cloud 18th

The filament forming an electrically conductive channel with ions. These ions form condensation nuclei around which raindrops form around. by

And self-focusing of the laser beam can -defokussierung the filament extend without substantial divergence over large distances, eg up into a cloud, and there to the formation of condensation nuclei to take effect.

This condensation nuclei can first to detect an over-saturation of the

Atmosphere with water vapor serve. The detection of condensation nuclei can with known methods, eg by LIDAR technology ( "McGraw-Hill Encyclopedia of Science & Technology" Bd.10, page 40) or Mie scattering done. Mie scattering is known to be a scattering of aerosols or particles whose dimensions are in the order of the wavelength of light (Bergmann-Schäfer, "Textbook of

Experimental Physics "Vol. 3." If condensation nuclei are detected Optics "9th Edition, page 421)., There is a supersaturation, wherein a gradation (none, medium, high supersaturation) may be determined.

By knowing the degree of supersaturation several produce different

Applications: The degree of supersaturation can be recorded for purely meteorological applications. but it can be taken in order to achieve an early raining clouds various measures. This can be done to prevent hail formation. but it can also happen to produce rain in a desired area. The measures may include the above-mentioned use of silver iodide. but the rain can be here presented also by the filament itself by the condensation nuclei produced by the filament is a

bring rain down.

In Figure 9 90 designates a laser device for generating Laseφulsen 22, with a frequency of about 10 Hz, the duration of the order of femtoseconds and whose direction is in the order of Terawatts. This Laseφulse 92 are directed through a telescope 94 in a beam 96 upwardly into the atmosphere. Here, the Laseφulse a "filament" 98 is formed due to the high power density due to self-focusing due to the Kerr effect in air and Selbstdefokussierung by ionization of the air. The laser beam is guided largely by the formed in the air, alternating "converging and diverging lenses" without divergence in a very narrow cross-section of eg 0.1 mm cross-section and may be to high km above the atmosphere in a range between 80 and 120 Height extend. The filament produces white light, that is a continuum which extends over a very wide wavelength range. This white light is irradiated substantially only in the direction of the laser beam and the filament back to the front and in the opposite direction along the laser beam or filament. The white light is indicated in the figure by arrows 100 and 102, the arrows 100 denote the emitted white light to the front.

In the region 104 above the actual atmosphere 106 is called. "Meteroitenstaub". These are suspended particles of different elements, which have their origin in meteorites, which were vaporized on impact with the atmosphere and atomized. By the white light of this meteorite dust is excited to fluorescence. The excited by the white light meteorite dust forms an artificial light source, indicated in the figure by the 108th

The laser beam and the filament is pulsed in the manner described above. Accordingly, the filament also provides pulsed white light, which in turn causes the artificial light source 108 is pulsed accordingly. By a sensor 110, the backscattered light pulses of the pulsed light source 108 are detected. These light pulses are temporally compared to the emitted Laseφulsen. Hence the term of the transmitted and backscattered light pulses is determined. This is illustrated in the figure by block 112th The runtime returns along the laser beam 96 and

Filaments measured distance of the artificial light source 108 and thus its exact position. This is illustrated by block 114th

In the figure, a telescope is aligned with the artificial light source 108 1 sixteenth From a comparison of the observed from the telescope position of the artificial

Light source with the real position can be determined 16, which are caused by the atmosphere 106 aberrations, including distortion of the telescope. 1 Such aberrations can then be taken into account 1 18 in the observation of a lying approximately in the same direction celestial object.

Claims

claims
1. A method of influencing of matter at a great height from the ground, characterized in that the influencing takes place by means of a signal generated by self-focusing high intensity laser beam and -defokussierung directed against the sky filament.
2. The method according to claim 1 for the production of condensation cores in the atmosphere comprising the steps of:
(A) generating a Laseφulses with a pulse laser,
(B) transmitting the Laseφulses from the earth in the atmosphere, and
(C) temporal and spatial focusing the Laseφulses such that the peak power of the Laseφulses at a location in the atmosphere, the critical
Power for self-focusing effect of the Laseφulses in air exceeds, so that a filament is formed by the Laseφuls.
3. The method according to claim 2, characterized in that a sequence is generated by Laseφulsen by the pulse laser.
4. The method of claim 2 or 3, characterized in that the pulse width of Laseφuls less than 10 "14 s.
5. The method according to any one of claims 2 to 4, characterized, in that the
Is output power of the pulse laser is greater than 10 11 Watts.
6. The method according to any one of claims 1 to 5, characterized in that the condensation nuclei are detected as an indication of over-saturation in the atmosphere.
7. A method according to claim 6, characterized, in that the detection of
is carried out by condensation nuclei lidar technology.
8. The method according to claim 6, characterized in that the detection of the over-saturation is carried out based on Mie scattering.
9. The method according to any one of claims 6 to 8, characterized in that in
Existence of supersaturation measures to premature raining be taken.
10. A method according to claim 9, characterized in that the premature
done by raining Aussteuen of silver iodide.
1 1. A method according to claim 9, characterized in that the cloud with the filament is acted upon as a measure for premature raining.
12. The method according to claim 1 for generating an artificial light source at a great height, characterized by the steps of:
(A) by generating a self-focusing and -defokussierung high intensity, pulsed laser beam (96) generated, directed towards the sky filament (98) having a white continuum radiation (100)
produces the longitudinal direction of the filament (98), by at height
Excitation of meteorites dust an artificial light source (108) occurs,
(B) measuring the pulse duration of the artificial light source (108) back-scattered light with respect to the emitted Laseφulse (92) of the pulsed laser beam (96) and (c) determining the real position of the artificial light source (108) from the direction of the filament (98) and the pulse duration of the artificial light source (108) back-scattered radiation.
13. Use of the method according to claim 1 for correcting errors caused by the atmosphere illustration of an astronomical 'telescope, characterized by the steps of:
to be calibrated (a) observing the artificial light source by means of the
telescope,
(B) determining the image supplied from the telescope of the artificial light source and
(C) correcting the images produced by the telescope with respect to imaging errors by comparing the real position of the artificial light source and the image provided by the telescope.
PCT/EP2002/011362 2001-10-12 2002-10-10 Method for treating material at a high altitude WO2003032710A3 (en)

Priority Applications (4)

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DE2001150211 DE10150211C1 (en) 2001-10-12 2001-10-12 Method for treating material at a great height from ground, directs filament towards sky after generation by automatic focusing and defocusing of a high-intensive laser beam
DE10150211.7 2001-10-12
DE2001150336 DE10150336B4 (en) 2001-10-15 2001-10-15 A method for generating an artificial light source at a great height, in particular for the calibration of astronomical telescopes
DE10150336.9 2001-10-15

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WO2008062441A3 (en) * 2006-09-10 2008-08-21 Shivshankar Kanhuji Chopkar Artificial rainmaking systems

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